Process for purifying naphthenic acids



. .trol euin Iractions.; I I

It has been customary to distil the naphthenic Patented Oct. 18, 1931s Iman ion;

This invention relates $6,. processfor treati g naphthenic acidsand ithas particular relation Naphthenic acidsgsuch aslmight he -obtainedfrom-the. alkali wastes arising'dnringtthe refining of petroleumorushale' oil'iractions, constitute a complex mixture of acidiccompounds jcontaining principally carbon, hydrogen and oxygen.-.'Theyrange from. comparatively low boiling liquids: to

materials which are solid2 or semi-solid at ordinarytemperatures.Their-viscosities as well as their boiling points are-directlyproportional-to the viscosities and :boiling points ofthe "hydroa 1carbon fractions in whichathey'were originally present... The crudenaphthenic acids which are derived :by acidifying alkali wastes formed"during the treatment of hydrocarbon fractions contain vary- 'ing amountsof carbonaceous materials. mWhen these crude naphthenic acids are "freedfrom phenolic materials by careful acidification and-tdistillation ashereinafter described,...this. quantity,

of carbonaceous materials appears to increase as a-result of which 3 to5% thereofand sometimes even greater havebeen found to be present in thedephenolized naphthenic acids. :The major portion or this carbonaceousmaterial exists in a is not removable bysettling or centrifuging andcauses the naphthenic acids to. be of a dark,

turbid color, :thereby, rendering :.their sale as a commerci'alproduetpractically impossible. Y I Theterm :alkali wastes,'occurring above, is40 meant to'include the productnwhich is obtained by treating with acaustic solutionthe extract resulting from a treatment of hydrocarbonfracacids to remove this admixed carbonaceousmaterial and then treat vthe overhead product to remove the dark coloration and: foulodor there afrom; This distillation was usually accompanied "by a plugging of thestill due to the presence of this undesirable material and the overhead,prodx I uct was not materially improved in color-,"i.--e.,

I have discovered that these-carbonaceous terials and color bodies maybereadily/removed without distillation by contacting the crude; or r1dephenolized acids whichiwill behereinafter des- IQ Fred crich'rfnsisrlrm enr,- csm.-;m|smax Union Oil Company of California, Los i II 1 perhaps, ,pentane, low boilinghydrocarbori frac tions,-. such. as Ipetroleum ether or' ,eleanefls .qnaphtha .(a, petroleum fraction-boilingbetween finely suspended: or colloidalstate', suchthat it ,4

' .benzoL- In general, ,the non-aromatic diluents mhave beenfQund-io bepreferable.

- latter with ,hotair orahot inert gals. j

- a The concentr'ation Q I the a91d used in my? process should =bepreerably such, that the car- 'tions with liquid sulphur dioxide as wellas any other alkaline wastes arising on refining, of petainingfinorganicacids,

phosphoric ,aeid, nitric ,acid,.] etc. j' such facids are added in,small amounts to naphthenic acids containing ca'rbonaceouslmaterials andthe mixture agitated for a short time, the carbona- I5 ceous materialsagglomerate gto sufllciently large par-ticles to permltseparation'bysettling. (H1188 furthermorebeenfound'that the naphthenlclacidsthustreated. .and which haveflsubsequently been I wat r Washed and q flstgro es y- 0 vproved color, a slightly 'higher lfacid'numberthantheuntreatedaaoids, are more fluidjand can be distilled to a 95%overhead without cokinglthe "bottoms, whereas I the untreated.ac'idsiparef lack and-opacu e,are;somewhat viscous and leavejja. 15coke-filled residue, when distilledto .95 %gov'erhead. Theaciditrea'tmentcan conveniently, and sometimes preferably be, carriedout on], naphthenic, acids Iwhioh have been dilutedwith' light@hydrocarbons in which case the sludge and'carbon I20 :settlesmorerapidly,,and in some casesmore .com-

. plet e1y perhaps due to a sludge precipitating I wtendency of the'light hydrocarbonsv in the latter instances. The light hydrocarbons-maybe subsequently removed by distillation orby extraction '26 i of thenaphthenic acids with alkali; Bytheterm Afl ght hyd rocarbons" I mean.any lowgboi ling :;h-ydrocarbonof either: a parafliniclor aromaticnature and it includesnormally volatile hydroe carbons, such as.propane, butane, isobutaneland 200.400 and aromatic hydrocarbons, such:as.

relates .to; ;the removal of finely 'susp'ended water from ahydrocarbon} fraction; by agitating the bonaceous material and color"bodies are] precipitated as-agran'ular mass Acids'of low concentrationtend to mulsifi'iiheiiaphthenic ac'lds ,whereas. highly eoncentratedacidstend' to be ,miscibl withthe, naphtlienici l'acid's relse react "wm m. a

. Thus, where sulphurie acidlhaving a concentraernulsion, a apparentlystabilized by the carbonaceous. materialj fi's obtained, These emulsionsI -pre s ent considerable dimcul'ty, in" their resolution not more thancould be traced'to the removal of v '55 thiscarbonaceous'materialitself. i

and should be avoidedlv "'I'hisemulsiQcatiQn troubleissubstantiallyovercome wherein'acid of 55 ,50% concentration' -or over is used;Sulphuric acid 1 of approximately 45%, strength jgave f'an emulsionwhich resolved jo n st'an ding for a short time. Concentrations betw en,215% and 50% can beused under some conditions' The mostjde .oo

,tion of 4.0%orlessisfusedi'ai'Pickering type of sirable range ofconcentration of sulphuric acid a (or anyofr the otheroxygen-containing-acids) was found to be from to approximately 83%.

Acids substantially in excess of 85% tend to bet-miscible with thenaphthenic acids while some sludge separation will occur/whenv they arecontacted with the latter, the treating loss becomes such thatthe'process is uneconom-. cu.

render them more susceptible to improvement in coloron su l nttreatment, such as distillation. V 1

.invention extends to the treatment of naphthenic acids with any oi theabove identiiiedinorganic acids in thepreseh'ce of a low boilinghydrocarbon solvent whereby aniore rapid and eiilcient purification isbrought about.

Although any oxygen-containing inorganic acid may for theofmyinventionjljprefer' to use acids such as sulphuric "acid, nitricacid or phosphoric' acid as they possess avery high .degree of stabilityand are very easily separable from the naphthenic acids after thepuriflcation has been completed. f I Therefore, more speciiicallmmyinvention ex- 1 tends to the use for the purpose at out-above oi theclass of ongen-containing inorganic acids of well defined concentrations(if desired in'the presence of ahydrocarbon diluent)' which conmt; orsulphuric acid, nitricacid and phosphoric I acid. I [1 a r fConsideringthe. process in greater detail, a

' caustic liquor such as might be obtained'by treatingj crude keroseneor a liquid sulphur dioxide extract thereof with hydroxide is acidiiiedin such a manner that it is only slightly acidic towardphenolphthalein.- By so operat- 'ing,the naphthenic acids, in contrastto the phenols, are not liberated from their alkaline Em-em saltsisodiumphenomenbut remain as sodium'naphthenates; The resulting mixture of 6"sodium naphthenates, pheno s and drocarbons is then'steam distilled, ifdesired in gthe presenceof a srnallamount of lldeleanu extractoran'analogousliliuid-hydrocarbomsuch 'as coaltar solvent-naphtha;'Thisextract may be the sameja'sthatfrom which the;phenols and Inaphthenic acids were obtained by the above described acidification andneutralization. The

"functionof this Edeleanuextract (oritsobvious 1 equivalents) is to'prevent frbthihgduring the distillation of the mixture of. sodiumnaphthenates, phenols and hy rocarbon oil. The distillation ofthislattermixtureywhich is preferably carried out in, the presence ofsteam, removes the phenols and hydrocarbon oils while the sodiumnaphthenates remain behind in the still. "esubstanuauy the acarbonaceous material:

which were present luv-the dephenoliaed naph- The sodium ,naphthenatesremaining as a residue after distillation of the above-described mixturewhen dissolved, in water and treated withsulphuric'facid, producenaphthenic acids *which containonly very small amounts of phenols andadmixed hydrocarbons. These crude naphthenic ".acids are of a' poorcolor and contain consider- I able amounts of, insoluble carbonaceousmaterial. The maJoi-"portion of this carbonaceous material and colorbodies which are present in line extract.- 2

1 materials.

process ofmyinventionz" thesecrude. naphth enic acidsin amountsvaryingfrom'2, to 5%. or Tevenjhigher, exists in a.

finely suspended or colloidal state such that it is not removable bysettling or centrifuging and constitutes a serious objection in themarketing -.or further "refining of the dephenollzed naphthen ic acids.

These naphthenic acids are then treated with ,;to,10"volumes per cent ofan oxygenino'rganic acid of suitable concentration, for instance,sulphuric acid. The mix- .ture'is agitatedfor'a brief period of timewhereupon-=the carbonaceous materials tend to agglomerate tosufliciently large particles to permit separation by settling. By addingsmall amounts of a "coking agent", suchas watersor siliceous@ea'rthimmediately after agitation of the naphthenic-acids with thesulphuric acid (or its equivalents) it is found that-the separation ofthe "sludgewhich comprises some free'sulphuric acid (or its equivalent)as well as the impurities which were present including all ofthe/suspended'carbonaceous material'and most of thecolor bodies, isgreatly facilitated. The thus refined naphthenic acids are separatedfromthe sludge and "coking" agent and are washed with water to removeany=remaining inorganic acidity. L They are-subsequently blown bright,preferably-with an" inert gas.. A materialiimprovement in the {color andacid number is brought 'about by this treatment. Should-any-additionalcarbon precipitate out on staridingfiit may beremoved by cellent producthaving a bland odor and-a stable color offrom 2to'3 N. P. A.is,obtained.-

The separation otxthe 'sludgeand carbonaceous materials in the abovedescribed separation may be materially improved --by. diluting theimpure -naphthenic acid'charge .beiore acid treatment with an equalvolume of a. hydrocarbon diluent I of the nature describeduabove. Incases. where such a diluent has been employed, the latter isseparated-from the sludge and carbonaceous materials together with thenaphthenic acids and or byextracting the naphthenic acids with alkaliand acidifying (with an inorganicacidithe" alka- As a modification orthe. above-described meth-" ad of operation in which specialprecautionswere cases where the presence of phenolic materials the naphthenicacidsis not'undeslrable. g f 1 The naphthenic acids, obtained'by thismethtogether with od, contain in addition to the phenols which arecompletely soluble therewith deflnite amounts of ,r. a; v e' ov Qii e tri a be carr outin a manner-identical to the one described in connectionwith the. naphthenic acids which had been substantially Thefoliowingeiramples are illustrative-.01 the may be removed. therefrom by simpledistillation freed irom phenolic lmm le r a chase of 1500 cubiccentimeters of semirefined naphthenic acids was air agitated forlb'minutes with 80% sulphuric acid.-. Just before theacid agitation wasstopped, 5 grams of diatomaceous earth were added to facilitate thecoagulation of the'sludge. The sludge (which contained only smallamounts of naphthenic acids) was removed from the supernatantnaphthenic, acids and the latter were washed with hot salt water; afterremoval of the wash water. they were blown bright with natural gas at atemperature of approximately 180 F.

The bright naphtheniciacids had anorganic distillation and a product wasobtained which Acid number-297 had the following properties:

milligrams of KOH per gram of substance. l

4 Color- 2- to 2 N. P. A. Odor-Sweet.

, A distillation, similar to the one described above was made onthesemi-reflned acids before acid treatment and the followingobservations were made:

(1) The semi-refined acids encyto plug up the outlet oflthe still.

(2) The overhead product from the acid treat-l ed naphthenic acids wasof a very much lighter ,color than that of the non-treated acids.

(3) The acid treated naphthenic acids could be distilledwithout crackingto a 97% overhead 1 (593 F. vapor temperature), while cracking occurredwith thenon-acid treated acids at 92% overhead (586 F. vaportemperature). 7 g

(4) The bottoms from the acid treated naphthenie acids were still fluidwhen cooled; those from the untreated acids were fairly hard inconsistency. l

. Example 11 'The following table illustrates at eflect of the adding ofa hydrocarbon diluent and of the amount of 60% sulphuric acidpn the timenecessary for sludge coagulation; v

' Time for Semil-eiined Cleaners 60% 'Agitation sludge to naphthcnicnaphtha, H150 number settle to acids in ml. ml. ml. of shakes compact Imass 50 50 5 150 10 sec. 50 25 5 150 30sec. 50 i5 5 150 1 min.

50 0 5 150 15min... 50 50 4 150 30 sec. 50 50 3 150 l min. 50 50 2 150 3min. 50 50 1 l 150 5 min. 50 0 3 150 20 min. 50 0 2 150 30 min.

This table is indicative of the fact that larger quantities of thesulphuric acid used (60%) tend to decrease the time of settling and alsothat an increase inthe amount of solvent for the same exhibited a tendjwhich they are present. l I

This invention is *not limited to any specific,

coagulation of the sludge; a i The amount of hydrocarbon diluenttcbe'used in facilitating the-separation of the coagulated.

carbonaceous material will be obvious *to those skilled in thevlilthough an amount equal 7 to that of the naphthenic acidcharge-to betreated been found practical in a number of instances, greater orlesseramounts may be necessary o'r convenient under certain conditions.

It hasbeen observed-that where the volume of w hydrocarbon diluent addedis greater than that of thenaphthenic acid charge, a better color isobtained with the same amount and strengthsof acid.

Other "coking" agents than the clay,ipreviously referred to,'may beu'sed.- Thus, small'amounts *of water may beadded to the naphthenic acidmixture immediately after agitation with the sulphuric acidor itsequivalents. However, "coking" agents-of the nature of clay or siliceousearth; a

are preferred as the naphthenic acids appear to have a somewhat brightercolor when the nonaqueous"coking";agent' is used. 1

The distillation of the 'naphthenic acids from though this distillationwill improve the color thereof, they'are' nevertheless'of 'such qualitythat they may be readily marketed a'commercial productil a I Althoughthis process has-been particularly described inconnection'with-naphthenicacids ad- 7 mixed-with carbonaceousm'aterialspit has been found that naphthenic acids which'are free fromthese materials or only substantially sc,:maybelrlateriallyimprovedthereby In suchcases, the refining action brought about by this-1process seems-to reside principally in an improvement in Odor, colorand acid number of'the naphthenic acids treated. 1 "*Thej naphtheni'cacids hereln described are: of'such a purity that they nlay be readilyused for commercial products, such as cosmetics, soaps, emulsifyingagents,- etc.

Instead of using an Edeleanu extract or, coal use any organic solventpreferably of an aromatic nature having a distillation rangesubstantially" that of the other solvents set out above.. r I While onlynitric, sulphuric and phosphoric acids have-been disclosed as examplesof oxygenobtained by; the process '1 tar solvent naphtha for theprevention of frothing during distillation of the mixture OLSOdIUm'naphthenates, phenols and hydrocarbon oil; in which process the'phenols'are removed, I may containing "inorganicacids; it has beenfound that H all oxygen-containing inorganic 'acidsare capa bleofbringingabout the purification of the naphthenic acids herein setforth. Thus, oxygencontaining inorganicacids other than those set for"the removal of carbonaceous materials or color bodies or-both fromnaphthenic-acids-in example herein set forth nor to'naphthenic-acidsderived mm any'particular hydrocarbon fraction "containing admixedcarbonaceous materials, the

"outabov'e, such as 'chloric', (H6103), bromic (Him-0:), and iodic acids(H101) may be used 25. which the carbonaceous materials havebeen removedmay bedlspensedwith if so desired. 1 Alhaving a concentration between 45and 85% and separating the naphthenic acids from the acid sludge-and thecarbonaceous materials which have been agglomerated-by theaforesaidsulphuric acid. ,1: i a

2. In' a process for purifying naphthenic acids contaminated withcarbonaceous materials and color bodies, thesteps of contacting saidacids with sulphuric acid having a concentration of 80% and separatingthe naphthenic acids from the acid sludge and the carbonaceous materialsand color bodies which have been agglomerated by the aforesaid sulphuricacid v 3. .Ina process for purifying naphthenic acids contaminated withcarbonaceous -materials, the steps of contacting said )acids withphosphoric acid having a concentration which is in excess of andseparating the naphthenicacids from the acid sludge and thecarbonaceousmaterial "which hasbeen agglomerated by the aforesaidphosphoric acid. a

4. In a process. for purifying naphthenic acids contaminated-withcarbonaceous .materials, the stepsof contacting said acids withanoxygencontaining, inorganic acid of such strength that .it is adaptedto agglomerate theaforesaid carbonaceous materials, adding a cokingagent to said mixture of naphthenic and oxygen-containing, inorganicacid and separating the naphthenic acids from the agglomeratedcarbonaceous materials, acid residueand coking agent. a V

:5. In aprocess for purifying. naphthenic acids contaminated withcarbonaceous materials, the steps of contacting said acids with anoxygenc'ontaining', inorganic acid of such strength that it is adaptedto agglomerate the aforesaid car bonaceousrnaterial, addinga coking?agent to said mixture of naphthenic acids andthe oxygencontaining,inorganic acid, separating the naphthenic acids from the agglomeratedcarbonaceous materials, acid residue. and coking agent, and washing theseparated naphthenic acids with a reagent adapted to remove any'residualinorganic acidity therefrom. a y 1 6. Ina process for purifying,naphthenic acids according to-clairn 5, theadditionalsteps of dis--tillingthenaphthenic acids which are free from inorganic acidity andcondensingthe overhead product.

7; A process for obtainingmaphthenic acidsof excellent color and whichare free-from admixed carbonaceous materials and color bodies comprisingthe steps of extracting a petroleum fraction with alkali, treating theresulting extract with an inorganic acid in such a manner that; only:the phenols admixed with the; alkali naphthenates in they aforesaidextract areiliberated, distilling the phenols overhead, liberating thefree crude naphthenic acids from the alkali naphthenates .re-

maining in thestill after. completion of the said distillationfor'removal of the phenols by adding an inorganic acid to the'saidnaphthenates, sepa rating the free naphthenic acids which containadmixed carbonaceous materials, contacting said free-naphthenic acidswith /2130, 10% by volume ,ofan oxygen-containing,inorganic acid of suchstrengththat it is adapted toagglomerate the k a 2,183,765 ms ofcontacting said acids with sulphuric acid aforesaid carbonaceousmaterials and separating the naphthenic acids from the agglomeratedcar-'bonaceous materials and acid residues.

8. A process for obtaining'naphthenic' acids. of excellent color andfree from admixed carbonaceous materials according to claim 7 in whichthe acid used is sulphuric acid of a concentration of more than and lessthan 85%.

9.*A- process for obtaining naphthenic acids of excellent color and freefrom admixed carbonaceous materials which comprises extractingapetroleum fraction with alkali, acid treating the resulting extract toliberate a mixture of impure -naphthenic acids, separating the impurenaphthenic acids which contain the aforesaid carbonaceous-'materials,contacting the said impure naphthenic acids with an oxygen-containing,in-

organic acid selected from the class consisting of sulfuric acid,phosphoric acid and nitric acid of a concentrationbetween approximatelyand 83% to agglomerate the aforesaid carbonaceous materials andseparating the naphthenic acids from the agglomerated carbonaceousmaterials and acid residue. a

10.A process for'obtaining naphthenicacids or excellent color and whichare'free from admixed carbonaceous materials, comprising the steps ofextracting a petroleum fraction with alkali, treatin such a manner thatonly the phenols admixed with the alkali naphthenates in the aforesaidextract are liberated, distilling the phenolsonly from the alkalinaphthenates, liberating the free crude naphthenic acids from thealkalinaphthenates remaining in the still after completion of the saiddistillation for removal "of the phenols by adding an inorganic acidthereto, separating the free naphthenic acids which contain admixedcarbonaceous materials, diluting said acids with a low boilinghydrocarbon fraction, contacting the diluted acids with to 10% byvolume'of' an oxygen-containing, inorganic acid, of such, a

strength that it is adapted to agglomerate the a aforesaid carbonaceousmaterials, adding a fcok: .ing agent to the acid mixture formed bycontacting the diluted naphthenic acids with the aforesaidoxygen-containing; inorganic acid, separating the naphthenic acids andhydrocarbon diluent from the agglomerated carbonaceous materials, acidresidue and coking agent, washing the separated naphthenic acids with areagent -ingthe resulting extractwith an inorganic acid adapted toremove any residual inorganic acidity therefrom, separating thenaphthenic acids and hydrocarbon diluent from the washing agent,distilling of! *the hydrocarbon diluent from the said naphthenates andfinally distilling the naphthenic acids. a

1l. In a process for purifying naphthenic acids contaminated withcarbonaceous materials. thesteps of contacting said acids with anoxygencontaining inorganic acid of the class consisting of sulphuricacid, nitric acid and phosphoric acid of a concentration betweenapproximately 50% and 83%.

12; A method as claimed in claim 4 in which the inorganic aoid'isconcentrated sulfuric acid.

FREDERICK J. EWING.

